(a) Field of the Invention
The present invention relates to a check valve of a cylinder head. More particularly, the present invention relates to a check valve of a cylinder head that controls an oil amount supplied to the cylinder head in accordance with oil pressure of a hydraulic pump.
(b) Description of the Related Art
Many components, such as an exhaust valve, an intake valve, a rocker arm assembly, and a cam shaft, are mounted at the cylinder head. Oil is supplied to the cylinder head in order to cool such components.
Generally, a hydraulic pump that supplies the oil to the cylinder head is connected to and driven by a crank shaft. The oil pumped by the hydraulic pump is supplied to the cylinder head through a main gallery of a cylinder block.
Since the hydraulic pump is driven by the crank shaft, as a rotational speed of an engine becomes faster, so does a rotational speed of the hydraulic pump. Therefore, oil supply of the hydraulic pump and oil pressure thereof increase as the engine becomes faster.
Generally oil supplied to the cylinder head must be maintained within a predetermined pressure range. If the oil pressure of the cylinder head is higher than or equal to a predetermined pressure, valve height and valve timing may change. Therefore, a valve train allowing for some degree of operating freedom has been designed such that the engine operates normally even if the oil pressure is higher than or equal to the predetermined pressure.
However, in this case, the valve train may be heavy and the cost may be raised.
In addition, even though the hydraulic pump must supply more oil than is needed in the engine, the hydraulic pump has been designed based on the minimum oil that the hydraulic pump should supply to the engine in the case that the rotational speed of the engine is low. Therefore, surplus oil that remains after being supplied to the engine is exhausted toward an oil fan.
Meanwhile, an orifice or a check valve has been used for controlling the oil supply to the cylinder head. The check valve has a spring for preventing the oil of the hydraulic pump from flowing backward when the oil pressure of the cylinder head is low.
If the orifice or check valve is used, the oil pressure supplied to the cylinder head can be lowered but in this case, the oil pressure supplied to the cylinder head may not be controlled in harmony with the oil pressure of the hydraulic pump.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.